Die cushion



Dec. 19, 1961 R. M. GOLD ETAL DIE CUSHION Filed Oct. 19, 1960 Ill m 0 7 r. A T? a. 0/ BE fiw United States Patent Ofihce 3,013,791 DE CUSHION Robert M. Gold and Herbert D. Carlson, Minneapolis, Minn, assignors to Dayton Rogers Manufacturing Co., Minneapolis, Minn., a corporation of Minnesota Filed Oct. 19, 196i Ser. No. 63,603 4 Claims. (Cl. 267-1) This invention relates to tandem pneumatic die cushions of the type employed in punch press machines and the like to absorb the impact of the press head.

Tandem pneumatic die cushions, which have been known in the past, have had several distinct disadvantages. One important disadvantage is the tendency of many die cushions to bind or retard movement of the upper cylinder because the upper cylinder tips or cocks with respect to the base or lower part along which the upper cylinder slides. Another important disadvantage of previously known die cushions is that difiiculty has been experienced in properly lubricating the moving parts.

With these comments in mind it is to the elimination of these and other disadvantages to which the present invention is directed, along with the inclusion therein of other novel and desirable features.

An object of our invention is to provide a new and improved pneumatic die cushion of simple and inexpensive construction and operation.

Another object of our invention is the provision of a novel tandem pneumatic die cushion which is constructed to permit the upper cylinder to vertically slide along the stationary parts without binding or otherwise having the movement thereof retarded.

A further object of our invention is to provide a novel and improved tandem pneumatic die cushion with the several moving parts thereof being well lubricated so that the die cushion will respond properly to impact pressure applied thereto.

These and other objects and advantages of our invention will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views and in which:

FIG. 1 is a section view taken on a vertical plane through the die cushion and being partly broken away; and

FIG. 2 is a detail section view taken approximately at 22 in FIG. 1.

One form of the present invention is shown in the rawings and is described herein. The pneumatic die cushion is indicated in general by numeral 9 and includes an upper cylinder 10 constructed of vrigid material such as steel and having a cylinder head 11 sealingly aflixed as by welding on the upper end thereof; The lower end of the cylinder llil is open and telescopically receives the base 12 therein. Base 12 has an exterior cylindrical surface 12a in interfitting relation with the inner cylindrical surface 1% of cylinder 14 The base 12 has a closed bottom 1212.

An upright piston rod 13 is affixed to the base 12 and extends upwardly therefrom. In the form shown, the lower portion 14 of the rod is formed integral-1y with the base 12. The upper portion of rod 13 is formed by a rigid tube 15, the lower end portion of which fits in a suitably provided bore 14a in the lower portion 14 of the rod and is threadably secured therein at 15a. An O-ring gasket 15b is provided between the tube 15 and the lower portion 14 of the rod. A piston head 16 is threadably secured at 16a to the upper end of tube 15, and the outer periphery 31 of the piston head slidably engages the inner peripheral surface 10a of the cylinder 19. The piston head 16 has an annular groove 16b extending around the entire periphery thereof and cooperates with the inner I periphery of the cylinder 10 to define a lubricant passageway. The piston head 16 is also provided with a sealing ring 1650 around its periphery to provide a seal between the head and cylinder.

The cylinder 19 is also provided with a second annular cylinder head 17 below the piston head 16. The annular head 17 has its inner periphery 17a slidably engaging the tube 15 of the piston rod and is sealed thereto by a cup gasket 17b. A sealing ring 170 is provided around the outer periphery of annular head 17 to seal against the cylinder 10. The annular head 17 is maintained in stationary relation with respect to the cylinder 1%) by an annular bead or key 18 which fits into a suitably provided notch or recess 7d of the head 17, and a retaining plate 1811 also bears against the head 18 and is afiixed to the head 17 by screws 18b.

in order to prevent formation of a vacuum between the annular head 17 and the piston head 16, an air port 19 is provided in the wall of cylinder 19 slightly above the annular cylinder head 17.

The piston rod 13 is provided with an air opening 26 extending longitudinally therethrough and through the upper end of the tube 15 and transversely through the lower end of the rod to provide air communication between the upper air chamber 21 and the lower air chamber 22.

A sleeve 23 is disposed in the opening 20, the lower end thereof rests upon a ledge 20a, and the upper end of sleeve 23 is retained by a retainer 23a which interfitsin a suitably provided groove in tube 15. The sleeve 23 has an annular spacer 23b afixed around its exterior at the upper end to maintain the sleeve 23 in spaced relation with the interior of tube 15 throughout substantially its entire length to define the annular upright supply passageway 24 for lubricant. The upper and lower ends of sleeve 23 are sealed to the piston rod by sealing gaskets 23c.

Lubricant is supplied to the annular passageway 24 through a supply opening 25 which extends to the exterior of the base and may be connected by means of fitting 25a to any suitable supply of grease lubricant. The piston head 16 has a plurality of substantially radially extending openings 26 which communicate at their outer ends with the groove 16b and which are aligned at their inner ends With corresponding openings 15b in the tube portion 15 of the piston rod in order to supply grease from the annular passageay 24 to the groove 16b.

The base 12 also has an annular groove 30 around its outer periphery to cooperate with the inner periphery of the cylinder 10 in defining a grease passageway and the groove 30 is supplied with grease through a fitting 30a and a conduit 3011 connected therewith, which is also connected by a fitting 30c to supply passageway 25.

An opening is provided at the lower portion of the base for connection with a suitable source of air under pressure.

In the use and operation of the present invention, the die cushion is commonly employed in a punch press Patented Dec. 19, 1961 machine. The bolster plate of the machine may overlie the cylinder head 11 and the pressure pins commonly employed in a punch press will also engage the cylinder head 11. A source of supply of air under pressure is connected at the opening 12c so as to create a pneumatic pressure in the air chambers 21 and 22. A supply of grease under pressure is connected to the fitting 25a.

When a downward force is applied to the cylinder head 11, the air pressure in the chambers 21 and 2.2 will tend to prevent any downward movement of the cylinder 19, but the air in the chambers will be compressed in relation to the magnitude of the downward force applied. The cylinder will move downwardly along the base 12 to move the cylinder head 11 toward the stationary piston head 16 and thereby decrease the size of the upper air chamber 21. Simultaneously, the annular cylinder head 17 moves downwardly with the cylinder toward the base to decrease the size of the air chamber 22 and thereby compress the air therein. Air Will readily flow through the piston rod between the air chambers 21; and 22 so as to maintain the air pressures therein in equilibrium. There will be a doubling effect because of the tandem arrangement of the air cylinders.

it should be particularly noted that the piston head 16 in the present invention is stationary, and the distance between the outer periphery of the piston head 16 and the outer periphery of the base 12 is substantial so that the cylinder 10 is well guided in vertical movement to prevent tipping or cooking of the cylinder which would tend to restrict or prevent free and easy movement of the cylinder 10. Because the cylinder 10 is prevented from tipping, impact on the cylinder head 11 will be absorbed by the movement of the cylinder, together with the compression of the air in the chambers and no excessive strains will be applied to the several parts of the apparatus. It will be noted that as the cylinder 10 shifts downwardly to the dotted line position B, the length of overlap between the base 12 and cylinder 10 is increased, and because the piston 16 which is disposed well above the base remains in its predetermined position, the positive guiding effect of the piston i6 and base 12 is accentuated during the movement of the cylinder.

It should also be noted that in order to provide for free and easy movement of the cylinder with respect to the piston 16 and base 12, the metal-to-metal contacts between these several parts are well lubricated by the supply of grease at the grooves 16!) and 30. Under pressure, the grease is supplied through the passageway 25 upwardly through the annular passageway 24 and then outwardly through the supply openings b and 26 to the groove 1612. By this means, grease is supplied internally and continuously to the necessary areas. It will of course be noted that grease is also continuously supplied to the groove 3% through the conduit 30b from the supply passageway 25.

When the downward forces are removed from the cylinder head, the air pressure in the air chambers 21 and 22 returns the cylinder 10 upwardly until the annular cylinder head 17 engages the piston head 16 which is positively retained in stationary condition on the piston rod.

it will, of course, be understood that various changes may be made in the form, detail, arrangement and proportion of the parts without departing from the scope of my invention which consists of the matter described herein and set forth in the appended claims.

What we claim is:

l. A pneumatic die cushion, comprising a stationary lower hollow upright cylinder having a closed bottom and an open top, an upright piston rod extending upwardly through the open top of said cylinder and being afiixed thereon, said rod having an elongate opening therethrough and communicating with the interior of said cylinder, means for introducing air under pressure into the interior of said cylinder, a stationary piston on said rod and being spaced above the open top of the lower cylinder, an upper cylinder having an open lower end and also having an inner periphery surrounding and slidably engaging the extcrior of said lower cylinder and the periphcry of said piston, said upper cylinder having a top cylinder head spaced above said piston to define a first air chamber between the piston and head and said upper cylinder also having an annular lower cylinder head affixed thereon below said piston, the inner periphery of said lower head slidably engaging the piston rod and cooperating with said lower cylinder to define a second air chamber. t

2. A pneumatic die cushion, comprising a stationary base having a cylindrical exterior surface, an upright piston rod extending upwardly from the base and being afiixed to the base, said rod having an elongate opening extending through the upper end thereof and also extending through the rod adjacent said base, a piston head affixed to said rod and disposed in spaced relation above said stationary base, a hollow cylinder having an open lower end telescopically receiving said base therein and having an inner peripheral surface surrounding and slidably engaging the periphery of the piston head and the cylindrical surface of the base, said cylinder having an upper head sealingly secured around the cylinder and cooperating with said piston head in defining a first air chamber, said cylinder also having a second annular cylinder head sealingly fixed on the inner periphery thereof below said piston and spaced from the base, said annular head having an inner periphery slidably engaging said piston rod and cooperating with the cylinder and base to define a second air chamber, and means for introducing air under pressure into one of said air chambers.

3. A pneumatic die cushion, comprising a stationary base having a cylindrical exterior surface, an upright piston rod extending upwardly from the base and being affixed to the base, said rod having an elongate air opening extending through the upper end thereof and also extending through the side of the rod adjacent the base, a piston head affixed to the rod and disposed in spaced relation above said stationary base, a hollow cylinder having an upper end with a cylinder head sealingly affixed thereon and having an open lower end telescopically receiving said base therein and an inner peripheral surface surrounding and slidably engaging the periphery of the piston head and the cylindrical surface of the base, said piston head having a continuous groove around the periphery thereof and cooperating with the inner periphery of the cylinder to define a lubricant passageway, said piston rod having means defining a lubricant supply passageway extending longitudinally therethrough and having a closed upper end, said piston rod and piston head having aligned lubricant supply openings respectively communicating with said supply passageway and said groove, and said base also having a lubricant supply opening communicating with said supply passageway of the rod and communicating with the exterior of the base at a position below said cylinder, and an annular cylinder head affixed on the inner periphery of the cylinder below said piston head and spaced above the base and in sliding relation with said piston rod.

4. A pneumatic die cushion, comprising a stationary base having a cylindrical exterior surface, an upright piston rod extending upwardly from the base and being affixed to the base, said rod having an elongate opening extending through the upper end thereof and also extending through the side of the rod adjacent the base, an elongate sleeve in said opening and spaced inwardly of the opening to define an annular passageway at the exterior of the sleeve, means within said opening and at the exterior of the opposite end of said sleeve for sealing and securing the sleeve in stationary relation with the rod, said base having a flow passage extending from said annular passageway to the exterior of the base, a piston head affixed .on the upper end of the rod and spaced above the base, a hollow cylinder having a cylinder head on the upper end thereof and also having an open lower end telescopically receiving the base and piston head therein and also having an inner peripheral surface surrounding and slidably engaging the periphery of the piston head and the cylindrical surface of the base, said cylinder defining a first air chamber above the piston head, said piston head having an annular groove in the periphery thereof, the head and rod having aligned openings respectively communicating with the groove and with the annular passageway, a second annular cylinder head sealingly atfixed to the inner periphery of the cylin- 6 der below said piston head and above the base, the inner periphery of said annular head slidably engaging the rod and cooperating with the base in defining a second air chamber, and means in the base for introducing air into the second air chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,351,843 Dunn Sept. 7, 1920 1,434,949 Glasner Nov. 7, 1922 2,819,061 Platou Ian. 7, 1958 

